Interior free-flowing packaging materials, or "dunnage" as they are otherwise known, vary greatly in size and shape. The quality of any dunnage material for packaging purposes is dependent on certain functional characteristics. Among the desirable qualities in any free-flowing dunnage material are structural strength, low density and volume maintenance. Ideally, the material should also be lightweight, easy to use, versatile for use with any packaged product or with any type of container, non-settling, reusable and static-free. Primarily, dunnage material should have the necessary characteristics to prevent movement of the product within the container and to prevent contact between the product's surface and the interior surfaces of the container.
Foamed plastic materials have dominated the packaging and dunnage material markets. Foamed plastic products tend to be lightweight and homogenous across any cross section but tend to have certain disadvantages in handling, such as excessive static problems.
Furthermore, environmental concerns have raised considerable questions regarding the use of foamed plastic as a dunnage material. Plastics are not biodegradable and non-static. There are numerous examples of inventions for free-flowing plastic dunnage. A few examples of these inventions are disclosed in Skochdopole et al., U.S. Pat. No. 3,723,240, Fuss, U.S. Pat. No. 3,855,053 and Skochdopole et al., U.S. Patent No. 3,933,959. Despite the overwhelming use of plastics as the favored material for free-flowing dunnage products, one attempt appears in the prior art to use pulp fiber as dunnage.
McCrea, U.S. Pat. No. 4,997,091, teaches the manufacture of free-flowing pulp dunnage by extruding pieces of paper fiber and allowing them to dry into solid shapes. However, solid pulp is a heavier material than solid foamed plastic, resulting in greater shipping costs. Consequently, despite all of the aforementioned disadvantages in using foamed plastic as a dunnage material, foamed plastic continues to dominate as the favored material used in the manufacture of free-flowing dunnage.
Molded pulp has been previously used to manufacture containers and other form packaging, such as egg cartons and the like. The manufacturing process for form packaging is distinct from the invention. First, waste paper and water is mixed together to produce a pulp slurry. Forming dies are then immersed in the pulp slurry and a vacuum system causes the deposit of pulp fibers on a forming die. A puff of air from the forming die and a vacuum in the transfer die gently cause the wet formed products to lift off of the mold and onto the transfer die. The wet formed products are typically about seventy-five percent water at this stage and pass through a drying oven where hot air is employed to evaporate most of the remaining water content of the product. This process creates products which are hollowed out and uniform in shape and size. This uniformity enables the products to nest on one another.
This nesting tendency of molded pulp products manufactured by the foregoing process is not advantageous for a dunnage material. Nesting of the dunnage could result in a loss of volume maintenance within the shipping container, thereby providing less effective packaging protection.
The prior art recognizes that free form drying of pulp products will result in significant warpage. R.I. Reifers, U.S. Pat. No. 3,185,370. However, this warpage effect is consistently viewed as a substantial disadvantage in product manufacture. The prior art also does not disclose the formation of random beaded edges on the warped product. It furthermore does not teach the manufacture of pulp dunnage by a molding process or the manufacture of molded pulp products without the use of transfer dies.